1. Field of the Invention
The present invention relates to an image forming apparatus capable of remote maintenance of an electronic copier for reading and printing an original image on paper, in which the maintenance program or the like can be modified after shipment of the apparatus, and relates to a method of remote maintenance of an image forming apparatus.
2. Description of the Related Art
In an image forming apparatus such as an electronic copier, an original placed on an original glass (original rest) is irradiated with an exposure lamp, and a latent image corresponding to the original is formed on a photosensitive drum by the light reflected in the exposure process. The latent image is developed by a toner in a developing unit, and a toner image thus developed is transferred onto the paper using a transfer unit. After that, the toner image on the paper is fixed using a fixing unit.
It is well known that an image forming apparatus is composed of many mechanical parts and chemical materials, which are consumed and the properties thereof steadily deteriorated by repeated operations. Typical examples are a paper feed roller, a photosensitive drum, a developing material, a fixing roller and a fixing silicon roller.
In order to maintain the image forming apparatus in a superior operating condition, it is important to change these parts at an appropriate time before the properties thereof are so deteriorated that the image forming apparatus comes to malfunction. For this purpose, various techniques have been incorporated in the conventional image forming apparatuses.
A first method is to install a counter on an image forming apparatus for counting the number of operations performed by the image forming apparatus. This method is intended to detect the number of operations of the image forming apparatus by the operation counter and thereby allow the photosensitive drum, the developing material, the fixing roller, etc. which is considered to operate the same number of times as the image forming apparatus proper to be replaced before reaching their service life. This method, however, has the disadvantage of low maintenance efficiency in that unless the person in charge of maintenance actually checks the counter at the installation site of the image forming apparatus, the time of replacement cannot be determined. The methods described below have been proposed for obviating this problem.
A second method is to monitor the number of operations of the image forming apparatus from a remote computer through a telephone line or a data bus line. This method makes it possible for the maintenance person to check the operation counters of a multiplicity of image forming apparatuses in sedentary fashion. It has thus become possible for the maintenance person to attend an image forming apparatus only when required to replace predetermined parts. In spite of this, this method has a problem, and various suggestions have been made to solve the problem. A typical problem is encountered in checking the service life of the paper feed roller and the number of operating errors. Specifically, in the case of an image forming apparatus having a plurality of paper feed means, the number of operations of the operation counter fails to coincide with that of the paper feed roller. A method to overcome this problem is described below.
A third method is to install a paper feed counter capable of performing and monitoring the operation of incrementing the count each time paper is fed from each paper feed means. This has made it possible to grasp the consumption of each paper feed roller accurately. Nevertheless, a succession of problems have henceforth have arisen.
As the wear of the silicon roller progresses, for example, silicon oil is supplied in a lesser amount and the jamming rate in the fixing unit increases. Field study shows that silicon oil is consumed earlier for some users than for others, i.e., before the number of operations generally considered normal. The reason is unknown, and the result is often an increased jamming rate in the fixing unit. It is difficult to monitor this situation simply by the number of normal operations. In an attempt to meet this adverse situation, the following-described method has been proposed.
A fourth method is for a counter to increment the count according to a predetermined error code each time an operating error occurs, and to monitor the count.
This has made it possible to grasp the wear of the fixing silicon controller.
As described above, various improvement efforts have hitherto been made in order to secure an accurate and effective method for conducting preventive maintenance of an image forming apparatus.
Nevertheless, a completely satisfactory preventive maintenance technique has yet to be established for the image forming apparatuses. This is attributable to the fact that the image forming apparatus is made up of mechanical and chemical parts and materials having wear and fatigue characteristics which are still clouded by many unknown facts.
More specifically, the following problems still remain to be solved.
First, the conventional fixing silicon roller has so far been considered to consume oil only when the fixing unit actually operates and the roller functions to discharge silicon oil. The silicon oil consumption by vaporization and hence the deterioration of the silicon roller characteristics, therefore, has been considered negligibly small while the fixing unit is allowed to stand. It has become apparent, however, that this vaporization phenomenon is not to be neglected even for the users who rarely operate the image forming apparatus and that the causes of oil vaporization from the apparatus in waiting mode must be evaluated and calculated more positively as a parameter for sensing the characteristic deterioration of the parts.
A specific machine allowed to stand for an hour has been found to vaporize as much oil as would be consumed for producing about five copies on the average.
Secondly, the surface of the conventional fixing rollers is known to wear as it is rubbed by a pawl or the like while in rotation. It has so far been considered that this phenomenon is the primary cause of the deterioration of the fixing roller and the other factors can be virtually ignored.
A fact-finding survey of the market, however, has revealed that the fixing roller of the image forming apparatus installed in the premises of infrequent users is deteriorated in proportion to the length of time the fixing roller is allowed to stand in wait mode rather than by reason of the surface wear caused by the friction described above. This is due to the fact that since the fixing roller is left to stand for a long time in high-temperature wait mode, the adhesive used for joining the aluminum stock tube of the fixing roller with the teflon material coating the fixing roller surface comes off as the properties thereof are deteriorated by thermal stress. As a result, the surface coated material peels off before the lapse of a predetermined length of time (before the surface coated material is worn) having nothing to do with the number of actual copying operations. The fixing roller thus is considered to face the end of the service life thereof due to an adverse phenomenon which has hitherto been inconceivable.
The foregoing is a prediction of the deterioration of a fixing roller and a fixing silicon roller which is effective only to the extent of the currently-available knowledge. The knowledge presented above regarding the service life of the consumable parts is nothing but the technical one relating to the parts, and it is difficult to specify parameters having a deterministic effect on the service life. In order to find the real factors affecting the service life of the parts, therefore, it has been necessary for us to repeatedly compare the actual manner in which the fixing roller is operated with the actual length of time it is used.
This task has required the collection and analysis of lots of data over a long period of time, followed by repeated collection and analysis under the data measuring conditions corrected based on the result of previous analysis. Even the above-mentioned technique for monitoring the consumption of the fixing roller and the fixing silicon roller may become obsolescent any time in the future when a new, superior technique may be found.
Certainly, a superior method will be revealed in the future. At this time point, it is difficult to specify what is the future technique. It may become clear, for example, that the service life of the fixing unit is affected considerably by the accumulated time of temporary overshoots of the control temperature or the low- and high-temperature heat cycles. Such a problem could be readily obviated by a small correction of the technical specifications slightly. Actual execution of the small correction, however, makes it necessary to incorporate a corresponding program in an image forming apparatus.
An attempt to collect various parameters and confirm a correlation, at least as a test case, between an estimated service life and the actual service life of a given part under various conditions of machine operation will fail unless a required control procedure is incorporated in the image forming apparatus in advance. An actual product, however, has only a limited program memory. Even though it is desirable to incorporate a parameter collection program in advance, a control procedure for effective data collection is virtually impossible to specify before shipping the product from the factory.
As described above, the problem of the conventional image forming apparatus is that the service life of the parts such as the fixing roller and the fixing silicon roller, the properties of which are deteriorated with the length of waiting time, cannot be accurately grasped. Therefore, successful preventive maintenance is impossible.
Also, once a product is delivered to the user, adding a program of a new specification (a program intended to estimate the time before a specified part is consumed by changing the data collection parameters from time to time in accordance with the prevailing conditions) to the apparatus requires a change in the control program and hardware and thus involves a program installation work on a very large scale.